"I am really proud and pleased because for me it is a nice opportunity to work for this club again," the Argentinian told liverpoolfc.tv yesterday.
"Rafa has shown his trust in me once again and I'll try to do the best for the club and do my best to repay him.
"It was a surprise to get the call because I was training with the youth team in Valencia and studying to finish my qualification to become a professional trainer.
"But when Rafa got in touch I knew I had to act quickly and after I had talked to my family and they told me they understood, it was a great opportunity that I could not turn down.
"I will try to do as much as I can for this club and I hope to enjoy working with the Liverpool players."